U.S. patent application number 11/668936 was filed with the patent office on 2008-07-31 for maintenance of valid volume table of contents.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Jeffrey R. Suarez.
Application Number | 20080183960 11/668936 |
Document ID | / |
Family ID | 39669254 |
Filed Date | 2008-07-31 |
United States Patent
Application |
20080183960 |
Kind Code |
A1 |
Suarez; Jeffrey R. |
July 31, 2008 |
Maintenance of Valid Volume Table of Contents
Abstract
A method maintains a valid volume table of contents (VTOC)
written to in a fast replication relationship. A fast replication
query is issued to a track in which the volume table of contents
(VTOC) resides. If the query determines that a background copy is
in progress, a volume having the track is designated as unusable.
An apparatus maintains a valid volume table of contents (VTOC)
written to in a fast replication relationship. A controller issues
a fast replication query to a track in which the volume table of
contents (VTOC) resides. If the query determines that a background
copy is in process, a volume having the track is designated as
unusable.
Inventors: |
Suarez; Jeffrey R.; (Tucson,
AZ) |
Correspondence
Address: |
INGRASSIA FISHER & LORENZ, P.C. (IBM)
7010 E. COCHISE ROAD
SCOTTSDALE
AZ
85253
US
|
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
39669254 |
Appl. No.: |
11/668936 |
Filed: |
January 30, 2007 |
Current U.S.
Class: |
711/112 |
Current CPC
Class: |
G06F 3/0619 20130101;
G06F 2201/84 20130101; G06F 3/0622 20130101; G06F 3/065 20130101;
G06F 3/0689 20130101; G06F 3/0637 20130101 |
Class at
Publication: |
711/112 |
International
Class: |
G06F 12/00 20060101
G06F012/00 |
Claims
1. A method for maintaining a valid volume table of contents (VTOC)
written to in a fast replication relationship, comprising: issuing
a fast replication query to a track in which the volume table of
contents (VTOC) resides, wherein if the query determines that a
background copy is in progress, a volume having the track is
designated as unusable.
2. The method of claim 1, further including reformatting the volume
to render the volume again usable.
3. The method of claim 2, wherein reformatting the volume further
includes removing a data set control block (DSCB) in lieu of
reformatting the entire volume.
4. The method of claim 1, wherein issuing a fast replication query
is performed prior to an intentional or inadvertent withdrawal of
the volume.
5. The method of claim 1, wherein issuing a fast replication query
is performed by a redundant array of independent disks (RAID)
controller.
6. An apparatus for maintaining a valid volume table of contents
(VTOC) written to in a fast replication relationship, comprising: a
controller which issues a fast replication query to a track in
which the volume table of contents (VTOC) resides, wherein if the
query determines that a background copy is in process, a volume
having the track is designated as unusable.
7. The apparatus of claim 6, wherein the controller further
includes a redundant array of independent disks (RAID) controller
device.
8. The apparatus of claim 6, wherein the fast replication query is
issued to the track through an interface connected to the
controller.
9. The apparatus of claim 6, wherein the RAID controller reformats
the unusable volume.
10. The apparatus of claim 9, wherein reformatting the unusable
volume further includes removing a data set control block (DSCB) in
lieu of reformatting the entire volume.
11. The apparatus of claim 6, wherein issuing a fast replication
query is performed prior to an intentional or inadvertent
withdrawal of the volume.
12. The apparatus of claim 6, wherein issuing a fast replication
query is performed using a combination of software or firmware
operational on the controller.
13. An article of manufacture including code for maintaining a
valid volume table of contents (VTOC) written to in a fast
replication relationship, wherein the code is capable of causing
operations to be performed comprising: issuing a fast replication
query to a track in which the volume table of contents (VTOC)
resides, wherein if the query determines that a background copy is
in progress, a volume having the track is designated as
unusable.
14. The article of manufacture of claim 13, further including code
capable of reformatting the volume to render the volume again
usable.
15. The article of manufacture of claim 14, wherein reformatting
the volume further includes removing a data set control block
(DSCB) in lieu of reformatting the entire volume.
16. The article of manufacture of claim 13, wherein issuing a fast
replication query is performed prior to an intentional or
inadvertent withdrawal of the volume.
17. The article of manufacture of claim 13, wherein issuing a fast
replication query is performed using a redundant array of
independent disks (RAID) controller.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates in general to computers, and
more particularly to a system and method of determining whether a
volume table of contents (VTOC) is valid prior to withdrawing the
volume in a fast replication relationship.
[0003] 2. Description of the Prior Art
[0004] Data processing systems often work with large amounts of
data and require mechanisms to manage the storage and archiving of
that data. For example, transaction processing systems typically
access large databases and log results such as transaction records
at a very high rate. The ability to quickly and reliably copy data
from one storage area to another enables the deployment of
efficient and reliable high-performance processing applications and
systems.
[0005] In addition to increased performance, fast replication
capable systems simplify the code complexity of I/O intensive
processes such as those conducted on large mainframe systems and
the like. System performance may also be increased in that support
for fast replication operations may be provided by low-level
drivers and devices that are optimized for performance.
[0006] Fast replication capable systems preferably support multiple
concurrent fast replication data transfers. Since the data transfer
may be deferred indefinitely, the act of initiating a fast
replication operation between a source and a target volume is often
referred to as "establishing a fast replication relationship."
Likewise, canceling a pending fast replication transfer may be
referred to as "withdrawing a fast replication relationship."
[0007] Without support for fast replication relationships,
conducting a point-in-time copy often requires that a system
suspend all tasks that access a source and/or target device. Since
many systems do not have explicit knowledge of the devices that
will be accessed by each task, those systems require suspension of
all tasks except for the task conducting the actual fast
replication operations. Suspension of the various tasks or
processes in order to conduct fast replication operations greatly
reduces the performance of multi-tasking systems.
[0008] One challenge of fast replication capable systems concerns
the integrity of the volume table of contents (VTOC) when a volume
is withdrawn from a fast replication relationship. The possibility
exists that, upon a withdrawal, either on an intentional or
inadvertent basis, the VTOC contains invalid data. The VTOC can
contain invalid data if, at the time data was being physically
written to the VTOC using a fast replication method, the volume was
withdrawn and the method was terminated midstream. Such an
intentional or inadvertent withdrawal can be detrimental to
applications or programs that later attempt to use this volume.
SUMMARY OF THE INVENTION
[0009] Therefore, what is needed are methods and apparatus for
maintaining, managing, and evaluating the VTOC in respective
volumes to ensure that the VTOC contains valid information. Such
methods and apparatus would preferably operate in a manner that is
efficient, reliable, and straightforward to implement.
[0010] In one embodiment, the present invention is a method for
maintaining a valid volume table of contents (VTOC) written to in a
fast replication relationship, comprising issuing a fast
replication query to a track in which the volume table of contents
(VTOC) resides, wherein if the query determines that a background
copy is in progress, a volume having the track is designated as
unusable.
[0011] In another embodiment, the present invention is an apparatus
for maintaining a valid volume table of contents (VTOC) written to
in a fast replication relationship, comprising a controller which
issues a fast replication query to a track in which the volume
table of contents (VTOC) resides, wherein if the query determines
that a background copy is in process, a volume having the track is
designated as unusable.
[0012] In still another embodiment, the present invention is an
article of manufacture including code for maintaining a valid
volume table of contents (VTOC) written to in a fast replication
relationship, wherein the code is capable of causing operations to
be performed comprising issuing a fast replication query to a track
in which the volume table of contents (VTOC) resides, wherein if
the query determines that a background copy is in progress, a
volume having the track is designated as unusable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order that the advantages of the invention will be
readily understood, a more particular description of the invention
briefly described above will be rendered by reference to specific
embodiments that are illustrated in the appended drawings.
Understanding that these drawings depict only typical embodiments
of the invention and are not therefore to be considered to be
limiting of its scope, the invention will be described and
explained with additional specificity and detail through the use of
the accompanying drawings, in which:
[0014] FIG. 1 is a block diagram illustrating a network system
representative of the environment wherein the present invention may
be deployed;
[0015] FIG. 2a is a block diagram illustrating a storage array
representative of the environment wherein the present invention may
be deployed;
[0016] FIG. 2b is a block diagram illustrating an example fast
replication compatible storage management system according to the
present invention;
[0017] FIG. 3 is a conceptual illustration of how a first storage
volume may be written to from differing storage volumes;
[0018] FIG. 4a is an illustration of a storage device having a
volume table of contents (VTOC) and the location thereof;
[0019] FIG. 4b illustrates a storage device including a data set
control block (DSCB) pointing to metadata on the storage
device;
[0020] FIG. 5 illustrates a first example method of operation
according to the present invention; and
[0021] FIG. 6 illustrates a second example method of operation
according to the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0022] Some of the functional units described in this specification
have been labeled as modules in order to more particularly
emphasize their implementation independence. For example, a module
may be implemented as a hardware circuit comprising custom VLSI
circuits or gate arrays, off-the-shelf semiconductors such as logic
chips, transistors, or other discrete components. A module may also
be implemented in programmable hardware devices such as field
programmable gate arrays, programmable array logic, programmable
logic devices, or the like.
[0023] Modules may also be implemented in software for execution by
various types of processors. An identified module of executable
code may, for instance, comprise one or more physical or logical
blocks of computer instructions which may, for instance, be
organized as an object, procedure, or function. Nevertheless, the
executables of an identified module need not be physically located
together, but may comprise disparate instructions stored in
different locations which, when joined logically together, comprise
the module and achieve the stated purpose for the module.
[0024] Indeed, a module of executable code may be a single
instruction, or many instructions, and may even be distributed over
several different code segments, among different programs, and
across several memory devices. Similarly, operational data may be
identified and illustrated herein within modules, and may be
embodied in any suitable form and organized within any suitable
type of data structure. The operational data may be collected as a
single data set, or may be distributed over different locations
including over different storage devices, and may exist, at least
partially, merely as electronic signals on a system or network.
[0025] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
present invention. Thus, appearances of the phrases "in one
embodiment," "in an embodiment," and similar language throughout
this specification may, but do not necessarily, all refer to the
same embodiment.
[0026] Reference to a signal bearing medium may take any form
capable of generating a signal, causing a signal to be generated,
or causing execution of a program of machine-readable instructions
on a digital processing apparatus. A signal bearing medium may be
embodied by a transmission line, a compact disk, digital-video
disk, a magnetic tape, a Bernoulli drive, a magnetic disk, punch
card, flash memory, integrated circuits, or other digital
processing apparatus memory device.
[0027] The schematic flow chart diagrams included are generally set
forth as logical flow chart diagrams. As such, the depicted order
and labeled steps are indicative of one embodiment of the presented
method. Other steps and methods may be conceived that are
equivalent in function, logic, or effect to one or more steps, or
portions thereof, of the illustrated method. Additionally, the
format and symbols employed are provided to explain the logical
steps of the method and are understood not to limit the scope of
the method. Although various arrow types and line types may be
employed in the flow chart diagrams, they are understood not to
limit the scope of the corresponding method. Indeed, some arrows or
other connectors may be used to indicate only the logical flow of
the method. For instance, an arrow may indicate a waiting or
monitoring period of unspecified duration between enumerated steps
of the depicted method. Additionally, the order in which a
particular method occurs may or may not strictly adhere to the
order of the corresponding steps shown.
[0028] Furthermore, the described features, structures, or
characteristics of the invention may be combined in any suitable
manner in one or more embodiments. In the following description,
numerous specific details are provided, such as examples of
programming, software modules, user selections, network
transactions, database queries, database structures, hardware
modules, hardware circuits, hardware chips, etc., to provide a
thorough understanding of embodiments of the invention. One skilled
in the relevant art will recognize, however, that the invention may
be practiced without one or more of the specific details, or with
other methods, components, materials, and so forth. In other
instances, well-known structures, materials, or operations are not
shown or described in detail to avoid obscuring aspects of the
invention.
[0029] Fast replication techniques such as IBM's Flashcopy.TM.
technology have been developed in response to the need for
efficient copying mechanisms within high-performance processing
systems. A fast replication operation gives the appearance of an
instantaneous copy, while the actual transfer of data is conducted
as a background process, or is deferred until the data to be copied
is about to be overwritten. With fast replication techniques,
applications may conduct data snapshots (point-in-time copies) and
continue processing rather than suspending operation while the data
transfers occur.
[0030] Referring to FIG. 1, a network system 100 is representative
of the environment wherein the present invention may be deployed.
The depicted network system 100 includes workstations 110 and
servers 120 interconnected via a network 130. The network 130 may
comprise a local area network and/or a wide area network.
[0031] The depicted network system 100 also includes one or more
storage arrays 140 interconnected with the servers 120 via a
storage network 150. In one embodiment, the servers 120 are
mainframe computers configured to conduct high bandwidth I/O with
the storage arrays 140.
[0032] FIG. 2a is a schematic block diagram of a storage sub-system
200. The storage sub-system 200 is a representative example of
sub-systems wherein the present invention may be deployed and is
one example of the storage array 140 depicted in FIG. 1. The
storage sub-system 200 includes a storage array 210 and one or more
controllers 220. In one example, the storage array 210 may include
a redundant array of independent disks (RAID) configuration. The
storage sub-system 200 may include a plurality of controller
modules 220 that achieve increased reliability through redundancy.
Additionally, the storage array 210 may also achieve increased
reliability by interconnecting multiple storage devices 230 via an
array loop 240.
[0033] In the depicted embodiment, the storage devices 230 are
interconnected with an array loop 240. The array loop 240 also
interconnects the controllers 220 with the storage array The array
loop 240 circulates communications in both directions to increase
reliability and throughput. In one embodiment, the array loops 240
are point-to-point loops such as those defined by the fibre channel
standard.
[0034] In the depicted embodiment, the controllers 220 each support
a host connection 250. The controllers 220 receive access requests
via the host connection 250 and service those requests by
transferring blocks of data to and from the storage array 210. The
blocks of data that are transferred to the storage array 210 may be
redundantly encoded to permit error detection and data recovery in
the event of failure of one of the storage devices 230. Typically,
the controllers 220 organize the storage devices 230 in a redundant
manner and present one or more volumes for use by a one or more
servers or hosts such as those depicted in FIG. 1.
[0035] In addition to connection and data redundancy, the
controllers 220 may support various types of fast replication
operations. Fast replication operations provide the appearance of
an instant copy between a source volume and a target volume within
a storage sub-system such as the storage sub-system 200. Fast
replication operations conduct data transfers from the source
volume to the target volume at the convenience of the storage
sub-system 200 without halting access to the source or target
volumes by an external device, such as a host or server.
[0036] Referring to FIG. 2b, a fast replication compatible storage
system 205 includes a fast replication capable controller 220, and
a server or host 120 with a storage management module 280, and one
or more storage devices 230.
[0037] The fast replication capable controller module 220
facilitates copying data from a source device to a target device in
a manner that appears instantaneous. The controller 220 includes a
transfer module 270 that enables the transfer of data between and
within devices, and a tracking module 260 that tracks the movement
and placement of the data. In one embodiment, the modules of the
controller 220 are software modules configured to conduct their
designated tasks.
[0038] In one embodiment, the modules of the controller 220 manage
data within fixed-sized regions of storage on the storage devices
230 such as sectors, cylinders, or tracks. In certain embodiments,
the devices 230 managed by the described modules of the controller
220 are logical devices or volumes, wherein the data is distributed
across multiple physical devices in a redundant manner.
[0039] The transfer module 270 coordinates data transfers between
source and target devices. In one embodiment, the transfer module
270 conducts handshaking with the storage devices 230 in a manner
that validates the reliability of data transfers.
[0040] The tracking module 260 tracks the movement and placement of
data involved in fast replication operations. In one embodiment,
the tracking module 260 uses bit flags to mark and unmark regions
containing data involved with fast replication operations. The bit
flags enable reliable fast replication operations including fast
replication withdraw operations.
[0041] According to the present invention, prior to withdrawing of
fast replication relationships of a volume (either intentionally or
inadvertently) which is being written to using a fast replication
method, a fast replication query can be issued to tracks in which
the volume table of contents (VTOC) resides. If the query
determines that the tracks are active fast replication writes
(i.e., a background copy is in progress), then the respective
volume can be designated as unusable and later reformatted. Once
the volume is reformatted, applications or programs that attempt to
reference the volume and/or VTOC are not negatively affected.
[0042] Referring to FIG. 3, a conceptual illustration 300 depicts
how a storage volume 330 can be written to from differing volumes
310, 320. Writes 340 demonstrate that the writes 340 can exist
separately from the writes 350 being made to the storage volume
330.
[0043] Existing convention does not distinguish between the two
writes 340, 350 that are being made when one set of writes that are
being performed includes most of the tracks (i.e., writes 340).
Performing a fast replication query on the VTOC tracks serves to
indicate whether all fast replication writes which are terminated
will have a negative affect on the usability of a respective
volume. If the writes 340 do not include VTOC tracks, then the
write 350 can be preserved according to the present invention.
[0044] FIG. 4a provides a conceptual illustration 400 of an example
storage volume 405 having a series of records 415, incorporated
into a respective track (e.g., Cylinder 0, Track 0) where a VTOC
label is integrated into the record 415. As illustrated, the VTOC
data set can be physically located anywhere on the volume 405. FIG.
4b conceptually illustrates volume 405 having an included data set
control block (DSCB) record 420 which points to metadata on the
volume 405. A fast replication query, according to the present
invention, can evaluate the physical location of the VTOC to
determine if a fast replication relationship exists.
[0045] If a fast replication query determines that metadata tracks
on a storage device where a VTOC record points to, where a VTOC
record can be a data set (e.g., DSCB, or any file that is
referenced from a VTOC), is currently the target of a FlashCopy
relationship (physical background copy is taking place of metadata
tracks), a method of reformatting could involve removing the VTOC
record (removing the DSCB) (as opposed to reformatting the entire
device). This method could be used when the VTOC tracks were
already physically written but the actual metadata tracks have not
been physically written.
[0046] Turning to FIG. 5, a first example method 500 of operation
according to the present invention, is depicted. In one embodiment,
method 500 is performed prior to the intentional or inadvertent
removal of a volume which is being written to in a fast replication
method. Method 500 begins (step 510) by the issuance of a fast
replication query (step 520) which can be performed by a controller
such as a RAID controller or other processing device. Additionally,
the controller can incorporate and execute software, or firmware to
perform the issuance task.
[0047] As a next step, method 500 queries whether a background copy
is in progress (step 530). If so, the respective volume at issue is
designated as unusable (step 550). The volume can then be
reformatted (step 560). Here as before, the entire device can be
reformatted, or the removal of the VTOC record can be accomplished
when VTOC tracks are already physically written but actual metadata
tracks have not been physically written.
[0048] If it is determined that a background copy is not in
progress (again, step 530), the respective volume is deemed safe to
withdraw (step 540). Method 500 then ends (step 570).
[0049] FIG. 6 illustrates a second example method of operation
according to the present invention. Method 500 as shown includes
the same steps as shown in FIG. 5, except that once the method 500
determines that a background copy is in progress (step 530), the
respective DSCB is removed from the VTOC and the volume is
essentially "quick" formatted (step 560) without the step of
reformatting the entire device. If a background copy is not
determined to be in progress, the volume is deemed safe to withdraw
(again, step 540), and method 500 then ends (step 570).
[0050] An advantage of implementing the present invention is that
one is able to subsequently reuse a respective volume at issue for
any type of read or write activity without any type of negative
implication due to the volume being placed in a completely usable
state.
[0051] A further advantage is if the respective volume being
written to using a fast replication method to an existing free
space extent is not being written to, a subsequent fast replication
write may want to be preserved and not be terminated by withdrawing
and terminating all fast replication writes that are taking place.
As a result, the efficiency of the storage system is maximized
while the system and method resolves usability and accessibility
issues associated with particular storage volumes.
[0052] Software and/or hardware to implement the method 500, or
other functions previously described, such as the described
issuance of a fast replication query, can be created using tools
currently known in the art. The implementation of the described
system and method involves no significant additional expenditure of
resources or additional hardware than what is already in use in
standard computing environments utilizing RAID storage topologies,
which makes the implementation cost-effective.
[0053] Implementing and utilizing the example systems and methods
as described can provide a simple, effective method of maintaining
valid storage volumes as described, and serves to maximize the
performance of the storage system. While one or more embodiments of
the present invention have been illustrated in detail, the skilled
artisan will appreciate that modifications and adaptations to those
embodiments may be made without departing from the scope of the
present invention as set forth in the following claims.
* * * * *